# Problem 1
# =========
# If we list all the natural numbers below 10
# that are multiples of 3 or 5, 
# we get 3, 5, 6 and 9. The sum of these multiples
# is 23.
#
# Find the sum of all the multiples of 3 or 5 below 1000.
LIM = 1000

ans3 = sum([n for n in range(3,LIM,3)])
ans5 = sum([n for n in range(5,LIM,5)])
ans15 = sum([n for n in range(15,LIM,15)])
print "-> ", (ans3+ans5-ans15)
